Embodiments of the present invention generally relate to electrical outlets. More particularly, embodiments of the present invention relate to systems and methods for a temperature-controlled electrical outlet.
There are a number of situations when it may be desirable to control the operation of a device based upon a temperature. For example, a thermostat in a house may be set to activate a furnace whenever the temperature inside the house falls to a point that is uncomfortable. Alternatively, the thermostat may activate an air conditioner when the temperature in the house gets too high. As another example, a space heater may be set up in a barn to turn on when the temperature falls below a certain level, or a water heater may be activated to keep a livestock water tank from freezing over.
Often, it is desirable to control a device that does not contain a thermostat. For example, a space heater in a barn may simply run when power is supplied to it. That is, the space heater runs when it is plugged in. Similarly, some deicers do not include temperature sensors to measure the water temperature, and instead heat the water when plugged in. Thus, it is desirable to be able to control a device based on temperature.
Some devices may contain thermostats to control their operation between pre-set temperatures. In the case of these thermostatically-controlled devices, it is often desirable to alter the operating range of the device. In these situations, the device may be controlled by an outlet that switches the electrical power to the device in accordance with the ambient temperature.
Typically, in a thermostatically-controlled device, a thermostat is placed in series with the electrical components of the device. The thermostat may include bimetal arms that serve as the electrical switch for the device, and no additional components are required. Thus, when a preset turn-on temperature is reached, the thermostat activates the flow of electricity to the electrical components. For example, a deicer with an integrated thermostat placed in a fluid is normally preset to turn on when the fluid temperature reaches a value approaching the freezing point and to turn off when the fluid temperature reaches a value tens of degrees above the freezing point.
Some existing devices include a remote electrical outlet that plugs into an existing outlet. The remote outlet contains its own thermostat and a relay to switch power based on the outside temperature. In those remote outlets, the thermostat functions similarly to those described above in thermostatically-controlled devices.
While these thermostatically-controlled outlets serve to alter the on/off points of the devices plugged into them, they suffer from the fact that their own internal thermostat is not adjustable. Thus, a different outlet with a different thermostat must be purchased if the user wishes to vary the temperature at which the device is energized.
Also, the on/off response of thermostats used in remote outlets will often vary over a temperature range of several degrees, thereby not correlating accurately or repeatably to the ambient temperature. Accurate and adjustable set points would greatly improve the versatility of a temperature-controlled outlet. Thus, it is highly desirable to be able to adjust the temperature set points and to more accurately track the temperature in a temperature-controlled electrical outlet.
For example, an outlet may contain a thermostat to activate a device, such as a livestock water tank, whenever the ambient air temperature falls to a point where freezing may occur. The following discussion assumes a freezing point of 32 degrees Fahrenheit (F.). In outlets with thermostats used to prevent freezing, the thermostat will normally turn on at around 40 degrees F. While the water will not freeze until it reaches 32 degrees F., the set point for turning on the thermostat is usually situated around 40 degrees F. to accommodate the uncertainty in accurately determining the set point during production. That is, the set points of a batch of thermostats designed to turn on at 40 degrees F. may actually have a spread of +/−7 degrees F. around that temperature.
The thermostats used are typically of the bimetal type. Typical turn-on/turn-off set points are around 40 degrees F. and 70 degrees F., respectively. However, the actual on/off temperatures of the thermostats are usually specified with a range of 5-8 degrees F. above and below these set points because, as mentioned above, the thermostat may have an actual spread of +/−7 degrees F. due to inaccuracy during production. While this range is necessary in order to keep the price of the thermostats down, it is not desirable from an operation standpoint since the device controlled by the outlet could be turned on when the water temperature is only 50 degrees F. with no danger of freezing. Operating a 1500 watt deicer, for example, can therefore be needlessly expensive.
As mentioned, because of the higher turn-on temperature, an outlet may energize a device such as a deicer to heat the water even on days when freezing conditions do not exist. For example, the temperature of the water in a livestock tank is directly affected by the surrounding air temperature. Thus, if the air temperature drops to 20 degrees F., the water will cool until it starts freezing at 32 degrees F. Since the air temperature has dropped below its 40 degree F. set point, the thermostatically-controlled outlet will turn on the deicer placed in the tank and heat the water to keep it from freezing. Suppose now, however, that the air temperature is 35 degrees F.—three degrees above freezing. The water will tend to cool down to that temperature but not freeze. However, once the air temperature drops below 40 degrees F., the outlet will energize the deicer to heat the water even though the water was never in danger of freezing. In that situation, energy will be wasted in heating the water.
Another problem is that the thermostat employed in the thermostatically-controlled outlet may exhibit hysteresis that negates its benefits. For example, consider a thermostat that turns on when the temperature drops to 35 degrees F. and turns off when the temperature rises to 45 degrees F., thus exhibiting a ten degree hysteresis. If the air temperature drops to 25 degrees F., the thermally-controlled outlet will be activated and a deicer plugged into it will be allowed to operate to keep the livestock tank from freezing. Suppose now, however, that the air temperature climbs to 39 degrees F. The tank is no longer in danger of freezing, but the deicer will still be allowed to turn on, thereby expending energy, because the deicer is set to turn on at 40 degrees F. and the thermally-controlled outlet is still activated since the air temperature has never climbed above 45 degrees F.
Thus, it is highly desirable to have an electrical outlet that is capable of making more accurate temperature determinations and of making intelligent decisions regarding temperature conditions.
Another problem with current thermostatically-controlled switches is that devices plugged into them, such as a deicer, may draw 10 Amps or more of current. As a connector is used, the contacts tend to get worn, thereby increasing the resistance at the contact point. With the thermostat located in close proximity to the contacts, the heat from the connections can influence the on/off operation of the thermostat with the result that the thermostatically-controlled outlet shuts off when it should actually be turned on. Thus, it is highly desirable to shield the temperature sensor in a thermostatically-controlled outlet from heat generated by the electrical contacts in the outlet.
A potentially hazardous problem is that existing thermally-controlled outlets are designed to be used indoors or in dry locations. The use of such outlets in livestock tanks, however, is almost always outdoors, where the device is exposed to the elements. The construction of the existing devices makes them susceptible to shorting out if exposed to water. Current systems, if protected at all, are typically placed within a water-resistant enclosure that must be opened when a device is plugged into it, negating much of the benefit of the enclosure. Thus, it is highly desirable to have a water-resistant outlet for outdoor use.
Thus, a need exists for a system and method of adjusting the temperature set points and to more accurately track the temperature in a temperature-controlled electrical outlet. In addition, a need exists for an electrical outlet that is capable of making more accurate temperature determinations and of making intelligent decisions regarding temperature conditions. Further, a need exists for a temperature-controlled outlet that shields the temperature sensor from heat generated by the electrical contacts in the outlet. Additionally, there is a need for a water-resistant outlet for outdoor use. Therefore, a need exists for systems and methods for a temperature-controlled electrical outlet.